Chausiku, one of the females, left her young with other animals of the species, climbed a tree and lay down in a nest.
“It is unusual for chimpanzees to sleep during the day,” explains Huffman.
Then something extraordinary happened.
Chausiku came down from the tree, took his son, walked slowly and with difficulty, followed by the group, until he sat down in front of a bush.
“The name of the bush is mjonso,” explained Mohamedi Seifu Kalunde, Huffman’s research assistant.
Kalunde is a renowned expert in the local jungle. He was trained by his parents and grandparents in the art of herbal medicine, the study of medicinal plants. “It is a very powerful and important medicine for us,” he says.
The plant, which in Portuguese is called vernonia (Vernonia amygdalina), is used in Tanzania to treat malaria, intestinal parasites, diarrhea and stomach pains.
Many other groups in tropical Africa and Central America – who know the herb by various names, but generally as “bitter leaf” – also use it to treat diseases such as malaria, schistosomiasis, amoebic dysentery and other intestinal parasites and stomach pains.
Chimpanzee Chausiku plucked some branches and removed the bark and leaves, which if ingested in large quantities can be lethal.
Vernonia amygdalina can be toxic, but some chimpanzees from Tanzania know that it can have healing effects – Photo: Getty Images via BBC
The interesting thing – besides not being a plant that is part of the feeding of these primates – is that Chausiku chewed the kernels and then spit out the fibers.
Did the chimpanzee do this not to feed, but to feel better?
In other words, was Chausiku deliberately using the herb as a medicine?
Chausiku went to sleep in his nest earlier than usual.
The next day, Huffman and Kalunde noticed that she was still feeling bad: she needed to rest often, moved slowly and ate little.
But everything changed about 24 hours after ingesting mjonso’s bitter sap. The chimpanzee ran through the forest until it reached a swampy meadow, where it devoured large quantities of figs, ginger marrow and elephant grass.
Chausiku with his son Chopin – Photo: MIKE HUFFMAN
The observations that Huffman and Kalunde made during those two days in November 1987 became the first documented evidence of an animal consuming a plant with medicinal properties and recovering later.
Had they discovered animal medicine?
While it is true that this was the first scientific evidence of self-medication in animals, Huffman emphasizes that it is not a discovery, but a “rediscovery” of something that some cultures have forgotten.
In Tanzania, for example, that deep connection with nature was still alive.
“We know from our tradition that sick animals look for plants to improve, so we use these plants to treat our diseases as well,” explained Kalunde.
The chimpanzee episode was not the first time that scientists observed what appeared to be self-medication in the animal kingdom.
More than a decade earlier, primatologist Richard Wrangham and his colleagues saw that chimpanzees often swallowed whole leaves without chewing. At the time, scientists wondered if animals did this to cure parasitic infections.
The team even coined the term zoopharmacognosy – from the Greek zoo (“animal”), pharmaco (“drug or medicine”) and gnosy (“knowledge”) – to describe the behavior.
Mike Huffman (right) describes his relationship with Mohamedi Seifu Kalunde (left) as ‘a mutual intellectual partnership’ – Photo: Mike Huffman
But they failed to prove that these leaves contained chemicals toxic to the parasites, or that chimpanzees were sick before or that they were cured after self-medicating. That is, there was still no evidence to prove self-medication.
Knowing this, Huffman got his biochemical colleagues to analyze Vernonia amygdalina. They discovered more than a dozen new compounds with antiparasitic properties.
In addition, the primatologist collected fecal samples from the Chausiku group and found that, after chewing the plant, the parasite’s eggs in the feces decreased by up to 90% in one day.
What’s more, subsequent observations showed that they tended to chew bitter leaves during the rainy season, when parasites were more abundant.
“This was the beginning of this journey that I embarked on 35 years ago or more,” says Huffman, a professor at Kyoto University in Japan. He ended up becoming one of the leading experts in animal self-medication.
Chowsiku and its bitter leaf plant were the key to further studies, which showed that the event was far from unique.
In fact, we now know that this type of behavior goes far beyond chimpanzees. Other mammals, birds and even insects treat their own illnesses in different ways.
Huffman needed to prove that chimpanzees knew what they were doing when consuming natural remedies – Photo: Getty Images via BBC
Huffman himself began investigating reports from another place in Tanzania, where monkeys had “the strange habit of picking up rough leaves, folding them in their mouths and swallowing them”.
“For years I looked for a system to properly study this type of behavior”, until I discovered “that in fact they were expelling parasites”.
Since the leaves are difficult to digest, they “decrease the amount of time it takes for food to pass through the intestinal tract”.
They were cleaning your digestive system. “In exactly six hours, they expelled the parasites.”
After discussing the matter with colleagues, a group of scientists began to investigate. Today it is known that there are 40 different species of leaves that 17 different populations of chimpanzees, bonobos and gorillas use to get rid of parasites.
And primates are not the only ones using this technique.
“Now we know that small mammals like the civet also bend and swallow leaves and expel parasites, and large mammals like the brown bear and the black bear are similar,” says the scientist.
Some macaws and parrots use clay to treat stomach pains; clay binds to toxins and removes them from the body – Photo: Getty Images via BBC
“Canadian snow geese, usually the youngest ones, also self-medicate before migrating in winter, when they go south and have a long way to go. They clean their systems before going through this long and stressful period without being able to to feed”.
Do butterflies use medicine?
“Last year, a really interesting observation was made in Borneo (an island in Southeast Asia): orangutans were chewing certain plants, but without swallowing them, just grinding them with their teeth until they formed a paste that was then rubbed for 15 to 20 years. 45 minutes, “said Kim Walker of the Royal Botanic Gardens in London.
“What is really interesting is that it was the same plant that the local human population used for joint pain.”
“There are many, many animals that use all kinds of drugs to treat their own pathogens and infections,” says Jaap De Rhoda, a biologist at Emory University in Atlanta, United States.
“But I was interested in understanding whether animals with smaller and more different brains from humans could also use forms of medication.”
When sick, the monarch butterfly protects its young with chemical compounds – Photo: Getty Images via BBC
Insects are a group of animals that have developed a wide range of different medication strategies.
An example is the monarch butterfly which, when it is still a caterpillar, can only eat dairy grass or dairy plants. These toxic plants contain chemicals called cardenolids.
Butterflies are immune to these toxic compounds, which accumulate in their system and protect them from predators. But, in addition, the species of milkweed that have higher concentrations of these elements end up defending these insects from a deadly parasite: Ophrycocystis Electroscirrha.
The question to be discovered is whether the monarch butterfly specifically looks for these medicinal species of milkweed when they are already sick.
“To our great surprise, we found a strong preference among infected monarch butterflies to lay their eggs on these medicinal plants that will reduce the infection in their future offspring. Those that are not infected, chose plants at random.”
And there is another fragile and small creature that has medical knowledge.
The bees spread a medicine in the hive, but the compound is also used in food – Photo: Getty Images via BBC
“Bees have different ways of treating their infections,” says De Rhoda.
“For example, they collect resin from trees, the sticky substance that trees produce as a defense. Bees mix the resin with their wax, use it in their hives and it is proven that this compound reduces the growth of all types of pathogens”, explains.
Not only does it serve as a defense in their homes, but “now they can also consume it, to reduce diseases in their own body”.
For De Rhoda, “one of the interesting things about this is to think that medicine is a profession that can evolve over time, but that can also be lost. And that is what we are seeing with bees”.
“Viscosity is irritating, so over the years, beekeepers have inadvertently eliminated this drug, selecting bees that used less resin.”
“Now we must rethink things and let the bees choose their own medicines, medicines they have been using for millions of years, because it can really benefit the colonies and, therefore, beekeepers.”
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